Yes, it should bottleneck in some cases. If really depends on what games you are playing.

I've overclocked it to 4.5Ghz, also overclocked GPU's to 1402Mhz and Memory Clock to 6105Mhz. Also running now 1866Mhz ram speed with correct timings.

Checking Stability at the moment. looks fine but, when i play games, GPU can go to 80-90% usage and CPU still at 25-40% usage.

you will never reach 100% cpu in games that only use 1-4 cores, which is the vast majority.

Compounded by the weak single core performance.

You are also adding up the burden of running 2 cards at once on top. So yes the cpu is the bottleneck.

so the question becomes which games do you want to play specifically?

Arma 3, H1Z1, BF3, CSGO, Dota 2, ARK, Skyrim and GTA VI think this is the most common titles i play arround the week. Also, i have another little problem and it's when i want to stress test GPU, it just doesn't works... It says the NVIDIA Kernel Mode Driver has stopped working and has recovered. This happens since i overclocked CPU and updated the RAM to 1866, checked timings and adjusted them, both are same and CAS 11. System is stable, i can game, play with SLI much better than before, but i just won't be able to run 3DMark or just Stress Test GPU with Aida64. Do you think this can be ram speed faulty ? Also, last night i changed the thermal paste of my both GTX680 since both were like stones instead of thermal paste rofl. Applied a new one, aftermarket one, Reduced the temperature in Load by 7-10º wich is really nice because the fans are running at much lower speed than before, because i had a custom fan settings due to the overheat, now they just in auto and not passing 80º on the top card, the other one, even on full load, it only hits 50º ^^ Thanks to both of you for your repplies, and awaiting a new one!